In Chinese tradition the east wind blows in spring, so
东风 is poetically synonymous with renewal and good fortune, the opposite of the cold, bleak
西风 'west wind.' The phrase
万事俱备,
只欠东风 ('everything is ready, only the east wind is lacking') comes from the Battle of Red Cliffs in 《
三国演义》, where Zhuge Liang allegedly 'borrowed' an east wind to enable the famous fire attack on Cao Cao's fleet.